Trim the French beans, toss them in a pan with boiling water and salt and boil without covering the pan. Whisk the eggs in a bowl, add the single cream the parmesan, a pinch of salt and a grind of pepper; mix well until all the ingredients make a smooth sauce and set aside.Once the French beans are cooked, remove them from the pan with a slotted spoon, drain them well and sieve them in a vegetable mill into a bowl. Cook the pasta in the bean’s cooking water.Once al dente drain the pennette. In the meanwhile in a large pan, melt the butter, add the French bean pure and flavour for a few minutes; add the egg sauce, mix well and toss the penne in it. Mix rapidly again, sprinkle a grind of pepper and serve immediately.